EP0964996B1 - Auxiliary starting device for a diesel engine and method for starting a diesel engine - Google Patents

Abstract

The invention relates to an auxiliary starting device for a diesel engine (1), comprising at least one electrically supplied heating device (14) to improve the starting characteristics of the diesel engine (1), an inverter device (7) with an intermediate circuit (7b) which has a higher voltage level than a vehicle electric system, an energy accumulator (12) for the heating device (14) which is charged from the intermediate circuit (7b) with a higher voltage than a vehicle electric system (8) and a heating control device (13) which controls the supply to the heating device (14) by extracting electrical energy from the energy accumulator (12). The auxiliary starting device is configured in such a way that the heating device (14) is supplied with energy extracted from the energy accumulator (12) at a high voltage. The invention also relates to a corresponding method.

Description

The present invention relates to a starting system for a Diesel engine.

The willingness of diesel engines to start takes off at low temperatures down. On the one hand, there is an increase in the frictional torque responsible. On the other hand, leakage and heat losses decrease when compressing the air, the compression end pressure and the compression end temperature so far that a start without starting aids is no longer possible. The temperature limit depends on it i.a. depending on the engine type. So have direct injection diesel engines with one-piece combustion chamber (hereinafter "DI engines" better starting behavior due to lower heat losses as front and swirl chamber engines, which have a split Have combustion chamber.

Usually with small-volume DI motors as well as motors split combustion chamber used glow plugs to improve the starting behavior to improve. The glow plug of the candle protrudes into the Combustion chamber or in the chamber of the engine. In addition to glow plugs glow plugs (in the narrower sense) are also common, i.e. With glow plugs exposed filament. In large-volume diesel engines the starting aid often on preheating the intake air with the help of electrically heated heating plugs or heating flanges.

To be able to start the diesel engine at low temperatures the heater, e.g. the glow plugs, from the vehicle battery fed with electrical energy, which is converted into heat becomes. The one available during this preheating process electrical power is determined by the maximum possible discharge current the battery is limited. This decreases with falling temperature, behaves in the opposite way to the power requirement as Function of temperature. A built in a glow timer Temperature sensor controls the duration of the preheating time required. The course of the preheating period - i.e. the onset of readiness to start - e.g. signaled by an indicator lamp going out.

Due to the limited feed power, the preheating time is With small-volume DI motors common today, about 2-5 seconds (with a cold start). This relatively long waiting time before If you are ready to start, there is a certain security risk in dangerous situations in which an immediate departure is required, as well as a loss of comfort.

DE 195 32 163 A1 and WO 97/08439 describe arrangements in which a starter's short-term memory also different High-performance consumers supplied. This is Consumers that are only used after the start.

Various suggestions for further developments have already been made made by preheating systems. DE 195 41 001 A1 is a Arrangement known, in which an annealing system with one opposite an on-board electrical system voltage increased voltage from a capacitor is fed. This is to ensure that the Starter battery for feeding an electric starter motor is not burdened by the annealing process.

From DE 37 13 835 A1 it is known to have a glow plug Diesel engine to operate with a surge Shorten heating time. As an example, the operation of 6 volt glow plugs mentioned with a voltage of 12 volts.

EP 0 420 379 B1 proposes glow plugs for a diesel engine to feed from a series connection of two capacitors, the be connected in parallel when charging. This parallel / series changeover circuit causes the glow plugs to be supplied with double Battery voltage.

As a general state of the art regarding a power supply DE 37 43 317 A1 is mentioned in the motor vehicle. You revealed dining from other consumers (i.e. no glow plugs or similar) from a DC link with an increased DC link voltage. A DC link with increased DC link voltage is e.g. also described in DE 195 32 163 A1.

The present invention aims to provide an improved starting system to specify for a diesel engine.

• einen drehfest mit der Kurbelwelle des Dieselmotors verbundenen und auf ihr sitzenden elektrischen Starter;
• wenigstens eine elektrisch gespeiste Heizeinrichtung zum Verbessern des Startverhaltens des Dieselmotors;
• eine zum Ansteuern des Starters dienende Wechselrichter-Anordnung mit einem Zwischenkreis, der auf einem gegenüber einem Bordnetz erhöhten Spannungsniveau liegt;
• einen zum Speisen von Heizeinrichtung und Starter dienenden Energiespeicher, der aus dem Zwischenkreis auf eine gegenüber dem Bordnetz erhöhte Spannung aufgeladen wird;
• eine Heizsteuereinrichtung, welche die Speisung der Heizeinrichtung unter Entnahme elektrischer Energie aus dem Energiespeicher steuert;
• wobei die Startanlage so ausgebildet ist, daß die Speisung der Heizeinrichtung und des Starters aus dem Energiespeicher bei erhöhter Spannung erfolgt.

According to claim 1, the invention provides a starting system for a diesel engine, which comprises:

• an electric starter non-rotatably connected to the crankshaft of the diesel engine and seated on it;
• at least one electrically powered heating device for improving the starting behavior of the diesel engine;
• an inverter arrangement for controlling the starter with an intermediate circuit which is at a higher voltage level than an on-board electrical system;
• an energy storage device which serves to feed the heating device and starter and is charged from the intermediate circuit to a voltage which is higher than that of the vehicle electrical system;
• a heating control device which controls the supply of the heating device while drawing electrical energy from the energy store;
• wherein the starting system is designed so that the heating device and the starter are supplied from the energy store at an increased voltage.

In practice, suggestions for feeding Glow plugs or similar Do not enforce from capacitor stores. Other suggestions that go with one of the glow plugs To feed the on-board battery obtained slight overvoltage shorten the required glow times, but have - so far evident - also not widely used. The present invention is based on the idea of a Energy storage for the heating device not with the vehicle electrical system, but with the intermediate circuit of a (explained in more detail below) To couple the inverter arrangement. The energy storage can charged to relatively high voltages with little additional effort become. The heating device can then be powered with relatively high performance. This allows much shorter times Preheating times (e.g. preheating times) than in the prior art. The Invention thus makes a contribution to increasing traffic safety as well as driving comfort.

It should be noted that the supply of the Heating device from the energy store preferably, but by no means mandatory, in the exclusive sense. So is it is possible that only a part of the feed energy goes to the energy storage, another part of the (on low voltage) Vehicle battery is removed. The feed can also only partially from the energy storage, too other times, however, entirely or partially from the on-board electrical system battery. If, for example, a further supply of the heating device after the start of the diesel engine (e.g. afterglow in the first start-up phase or glowing during overrun) can be supplied from a generator after the start. in all of these cases the feed energy is preferred DC link removed.

For the arrangement of the energy stores, two are advantageous Alternatives suggested: According to the first alternative Claim 2 is between the energy storage and the intermediate circuit a charging device is connected, which charges the Energy storage by taking energy from the intermediate circuit controls. In the simplest case, the energy store is opened the voltage level of the intermediate circuit is charged. The charger is then (in the case of a DC link) For example, designed as a switch, which the energy storage couple directly to the DC link and separate from it can. But it is also possible to increase the energy storage or lower voltages than that prevailing in the DC link To charge excitement. In this case, the charging device can be used as Step-up or step-down converter can be designed. In the case of one AC voltage intermediate circuit, the charger can also be designed as a rectifier.

In the second alternative according to claim 3, the energy storage directly connected to the DC link. Preferably acts it is usually a DC link existing memory (e.g. a capacitor), which is the voltage in the DC link even with a steep slope increasing current draw keeps almost constant.

According to claim 4, the energy store is preferably a capacitor storage and / or a short-term battery. The capacitor store is e.g. through a parallel connection several capacitors with sufficiently large capacitance. "Short-term battery" is a heavy duty, quickly discharged Battery understood as described e.g. in WO 97/08439 is. In particular, their discharge time is less than 7 Minutes, preferably less than 4 minutes. Under discharge time is the minimum time between full charge and discharge status understood at the highest permissible continuous load. The maximum discharge current is in particular more than 10 CA, preferably more than 15 CA. The power density is in particular more than 250 W / kg, preferably more than 300 W / kg. The short-term battery is preferably an alkaline secondary system, preferably a nickel / cadmium system or a nickel / iron system. The Short-term battery contains in particular sintered electrodes, preferably as sintered plates or sintered foil plates, or Fiber structure electrodes. The latter is the electrode for example from a three-dimensional polypropylene fiber structure.

According to claim 5, the heating device is preferably a glow plug (i.e. a candle with encapsulated filament), one Glow plug (with exposed glow wire), a heating plug and / or be a heating flange. While the first two directly the The last two serve to ignite the fuel Preheating the intake air.

Claims 6 and 7 give preferred values for the increased voltage level of the DC link. A voltage level is preferred, which is at the top of the low voltage range, in which there are still no precautions against touching conductors (Protection against accidental contact) must be taken. It is this by voltages greater than approx. 40 volts. Are particularly preferred much higher voltages, e.g. in the range of 200-400 volts. These allow the transportation of relatively large capacities at low Stream.

According to claim 8, the intermediate circuit is preferably a DC link. According to claim 9 the electrical machine serving as a starter also functions of a generator. This is advantageously a Three-phase machine. To operate as a starter, the Inverter electrical energy from a in the low-voltage electrical system arranged battery, e.g. with help of a Boost converter in the increased voltage level of the DC link, and converts the taken from the DC link Freely adjustable frequency energy in alternating or three-phase current Amplitude and phase around. It also generates in generator mode Inverter rotating fields. Since the current direction is reversed here is, however, electrical energy is generated by the electrical machine generated, which initially raised the intermediate circuit with its Voltage level and then, e.g. after voltage reduction, supplied to the low-voltage battery or other consumers becomes.

In addition to supplying the heating device, the energy store has Another function, and it serves to serve the electrical machine (although this is in a non-exclusive The meaning is to understand, so it is an additional feed can act). This is particularly advantageous in such Operating states in which the electrical machine has a high Has power requirement, such as according to claim 10 when starting or when they use the internal combustion engine when accelerating the vehicle supports ("electric booster") or temporarily the drive of the vehicle completely (in the manner of a Hybrid vehicle).

Fig. 1

ein Antriebssystem mit einem Dieselmotor und einem Ausführungsbeispiel einer erfindungsgemäßen Startanlage;

Fig. 2

ein Antriebssystem gemäß Fig.1 mit einer anderen Ausführungsform der Startanlage; und

Fig. 3

ein Flußdiagramm zum Starten des Dieselmotors mit Hilfe der in Fig. 1 oder 2 dargestellten Startanlage.

The invention will now be explained in more detail on the basis of exemplary embodiments and the attached schematic drawing. The drawing shows:

Fig. 1

a drive system with a diesel engine and an embodiment of a starting system according to the invention;

Fig. 2

a drive system according to Figure 1 with another embodiment of the starting system; and

Fig. 3

a flowchart for starting the diesel engine using the starting system shown in Fig. 1 or 2.

Parts that are functionally identical or similar have the same reference symbols.

The drive system according to Fig. 1 is e.g. for a motor vehicle, determined about a passenger car. It has a diesel engine 1, the torque via a drive shaft 2 (e.g. the crankshaft of the diesel engine 1), a clutch 3 and others (not shown) parts of a drive train on the drive wheels of the Vehicle. One sits on the drive shaft 2 as a starter, Auxiliary drive unit and generator serving electrical machine 4, here an asynchronous three-phase machine. It points you directly sitting on the drive shaft 2 and non-rotatably connected to it Runner 5 and e.g. supported on the housing of the diesel engine 1 Stand 6 on. The stator winding (not shown) 6 is by an inverter 7 with electrical currents and Voltages practically freely adjustable amplitude, phase and Frequency fed. It is a DC link inverter, which is essentially one constant DC link voltage with the help of electronic Switches e.g. cuts out sine-weighted width-modulated pulses, the - averaged by the inductance of the electrical Machine 4 - to almost sinusoidal currents of the desired Frequency, amplitude and phase lead.

The inverter is essentially made up of a machine DC-AC converter 7a, a DC link 7b and an on-board DC converter 7c built. The latter is with a vehicle electrical system 8 and an on-board electrical system long-term memory 9, here a conventional one Lead-sulfuric acid battery, coupled. The electrical system 8 and the Vehicle battery 9 are at a low voltage level, e.g. 12 or 24 volts. The intermediate circuit 7b is on the other hand an increased voltage, which is advantageously in the range between 200 and 400 volts. At high voltages are namely the semiconductor losses in the converter 7a are relatively small; further can the conductor cross-sections of the windings of the electrical Machine 4 can be dimensioned smaller than at low voltages. However, lower voltages are also advantageous, such as in upper part of the low voltage range, e.g. above 40 Volts. This can lead to full isolation Parts are dispensed with; on the other hand already the above advantages associated with higher tension noticeable. A capacitor 10 is connected in the intermediate circuit 7b, which the voltage in the DC link even with large Slope of rising current draw - that at generation of pulses from the converter 7a is present - approximately constant holds.

A charging device 11 is also connected in the intermediate circuit 7b, with which in turn a short-term energy storage device 12 is coupled is. It controls the current draw from the intermediate circuit 7b for charging the energy store 12. In the example shown the energy storage 12 to the same voltage level as the intermediate circuit 7b is charged, the charging device 11 functions So as a current control device, in the simplest case as a switch. at other (not shown) embodiments in which the energy storage 12 to higher or lower voltages than the intermediate circuit 7b is charged, it also has the function a voltage converter to higher or lower voltages. The energy store 12 is made of a parallel connection of capacitors high capacity built. Others (not shown) In embodiments, it consists of one or more short-term batteries. The energy store 12 is in turn via a Switching device 13, here in the form of power semiconductor switches, with a heater 14 that starts the diesel engine 1 relieved, connected. This is e.g. around one glow plug protruding into the combustion chambers of the diesel engine 1, and / or a so-called preheating plug, the intake air preheats.

The electrical machine 4 can after the starting process (in which it requires electrical energy), act as a generator, i.e. deliver electrical energy. In addition, it can be used as an electrical Boosters act, i.e. the diesel engine 1 at vehicle accelerations support. It can also - in the manner of a hybrid vehicle - temporarily take over the vehicle drive alone. The Converter 7c is designed as a bidirectional converter. He can on the one hand, when the electrical machine 4 is operated as a motor is and is fed from the on-board electrical system battery 9, electrical Energy from the on-board electrical system battery 10 in the intermediate circuit 7b bring, and on the other hand when operated as a generator is, energy from the intermediate circuit 7b for the purpose of supplying the consumer transfer the vehicle electrical system 8 and the vehicle electrical system battery 9.

The capacity of the energy store 12 is dimensioned so that it sufficient even at low temperatures to the diesel engine 1 for sufficiently preheat a safe start, e.g. preheat. With larger dimensions, the energy store 12 can be advantageous also serve the electrical machine 4 through the converter 7a to supply electrical energy. Particularly advantageous the energy storage device 12 is also used for electrical purposes Boosting required energy and the electrical Machine 4 briefly high electrical during vehicle acceleration To deliver power via the converter 7a. For the latter two Applications, the charging device 11 is bidirectional educated. That said, it can both draw electrical energy the intermediate circuit 7b in the energy storage 12 as well as in reverse Direction from the energy store 12 into the intermediate circuit 7b transfer and thereby possibly voltage increasing or -Degrading. A higher-level control unit 15 controls the inverter 7, namely the converter 7a and the converter 7c, and the charging device 11 and the switching device 13. Es gives the converter 7a amplitude, phase and frequency of those to be generated Three-phase voltage before. The converter 7c gives the amount of current the current direction and the amount of voltage step-up or step-down in front. The charging device 11 specifies which one Amount of current they take from the intermediate circuit 7b or into it should feed and feed the energy storage 12 or her should take. The control unit 15 also controls the switching device 13 and thus also the beginning and end of the heating process (e.g. of the annealing process). Among other things, it receives Input signals from one Temperature sensor 16, the information e.g. about the coolant temperature of the diesel engine 1 delivers.

2 corresponds to that according to Fig. 1. In contrast to the latter, however, the DC link capacitor 10 (or - alternatively - a fast one Battery) the function of the energy storage device 12. A charging direction is not available here. The intermediate circuit capacitor 10 is with sufficient capacity for its (additional) task as storage equipped for heating energy. Since it is directly in the intermediate circuit 7b sits, it is immediately at the voltage level of the DC link 7b charged.

The following is the function of the drive system with start system 1 and 2 explained with reference to the flow chart according to FIG. 3: In step S1, the energy store 12 is charged. The Charging takes place to a high predetermined value, which at Embodiment according to FIG. 2 (and possibly also in that 1) corresponds to the intermediate circuit voltage. It is done with the diesel engine 1 running from the one that then functions as a generator electrical machine 4. When the vehicle is stationary for a longer period the capacitor store 12 discharges gradually, however, so that it then in whole or in part by drawing energy from the on-board electrical system battery 9 is to be charged. The still existing in the energy storage 12 Amount of energy can e.g. just from the one he applied Voltage to be determined in readiness for a heating process, e.g. Stay pre-glow. Reloading takes in the Usually only take place after the engine has been idle for a long time, since the energy store 12 i.a. has been fully charged with engine 1 running, in other words, to a value that is higher than that required for starting Minimum value. The following will do this when the engine is not running Steps carried out: In step S2, the control device 15 determines the current engine temperature based on that of the temperature sensor 16 supplied measurement information and possibly the ambient temperature using an outside temperature sensor (not shown in FIG. 1). In step S3, the control unit 15 determines e.g. based on a saved Map that amount of energy, as expected at the temperature determined in the previous step (or with the determined temperature pair) for a successful start-up aid, e.g. in the form of preheating and / or preheating becomes. If the amount of energy still present in the energy store 12, the required amount determined in the previous step falls below, causes the control unit 15 in step S4 Recharging the energy store 12 by removing energy, which originates from the on-board electrical system battery 9, from the intermediate circuit 7b. The amount of energy still present in the energy store 12 can e.g. simply determined from the tension he still applied become. As a rule, reloading is only required after the engine has been idle for a long time take place, because the energy storage v.a. while running Engine has been fully charged, i.e. to a value above the minimum value required for starting aid. In step S5 asks the control unit 15 whether there is a command to start the diesel engine - For example, by pressing the start key has been. If this is not the case, the control unit 15 carries out the Steps S2 to S5 are repeated in order to save energy 12 to be constantly on standby, i.e. in a charge state, which is sufficient for a successful start-up aid. in the Step S6 causes the controller 15 to make the heater 14, (e.g. glow plugs) by closing the switching device 13 at short notice with very high output from the energy store 12 is fed. The total amount of heating energy is thereby in completely converted into thermal energy in the shortest possible time, so that very short preheating times of less than one second can be achieved. Finally, the diesel engine 1 is started in step S7.

Overall, the invention allows practically no delay Starting a cold diesel engine. The invention thus serves on the one hand, traffic safety, as they start faster allowed in case of danger, on the other hand it increases comfort. It can thus increase the acceptance of diesel vehicles. The Invention thus makes a contribution to environmental protection and Conservation of scarce resources.

Claims (10)

1. A starting unit for a diesel engine (1) having:

   an electrical starter (4) which is connected to rotate in unison with the crankshaft (2) of this diesel engine (1) and is seated on said crankshaft;

   at least one electrically fed heating device (14) to improve the starting behaviour of this diesel engine (1);

   an inverter arrangement (7) serving to control the starter (4), having an intermediate circuit (7b) which lies at an increased voltage level in comparison with an on-board power supply (8);

   an on-board battery (9), which is connected to the intermediate circuit (7b) via a voltage converter (7c);

   an energy accumulator (12), serving to feed the heating device (14) and starter (4), which is charged from the intermediate circuit (7b) to a higher voltage in comparison with the on-board power supply (8);

   a heating control device (13), which controls the supply of the heating device (14) in such a manner that a part of the supply power is removed from the energy accumulator (12) and another part from the on-board battery (9);

   in which the starting unit is designed so that the supply of the heating device (14) and of the starter (4) takes place at increased voltage.
2. A starting unit according to Claim 1, in which a charging device (11) is connected between the energy accumulator (12) and the intermediate circuit (7a).
3. A starting unit according to Claim 1, in which the energy accumulator (12) is connected directly into the intermediate circuit (7b).
4. A starting unit according to one of Claims 1 to 3, in which the energy accumulator (14) is a capacitor accumulator and/or a short-time battery.
5. A starting unit according to one of Claims 1 to 4, in which the heating device (14) is a heater plug, a sheathed-element heater plug, a heating-up plug and/or a heating flange.
6. A starting unit according to one of Claims 1 to 5, in which the increased voltage level of the intermediate circuit (7b) is above 40 volts, in particular above 100 volts.
7. A starting unit according to Claim 6, in which the increased voltage level of the intermediate circuit (7b) lies in the range between 200 volts and 400 volts.
8. A starting unit according to Claim 5, in which the intermediate circuit (7b) is a dc intermediate circuit.
9. A starting unit according to one of Claims 1 to 8, in which the electric machine (4) serving as the starter also has the function of a generator and in particular a three-phase machine.
10. A starting unit according to Claim 9, in which the electric machine (4) serving as the starter also has a function as a vehicle driving motor or auxiliary driving motor and is also fed completely or to some extent from the energy accumulator (12).

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